In hybrid vehicles each having an engine as a drive source and a generator motor mounted therein, a large-capacity capacitor such as an electric double layer capacitor is often used as the main power storage device. Such a capacitor characteristically has a large capacity and a long life, but also easily deteriorates if a full charge state or a nearly-full charge state continues. To prevent deterioration of the capacitor, there has been a known technique for moving part of the charges stored in the capacitor to an auxiliary power storage device with the use of a charge control unit at the end of an operation or the like (see, for example, Patent Document 1).
Patent Document 1: Japanese Patent Application Laid-Open No. 2005-218285